The Belle II Experiment and SuperKEKB Upgrade Wang, Boqun - - PowerPoint PPT Presentation

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The Belle II Experiment and SuperKEKB Upgrade Wang, Boqun - - PowerPoint PPT Presentation

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The Belle II Experiment and SuperKEKB Upgrade Wang, Boqun (University of Cincinnati) On Behalf of Belle II Collaboration September 26, 2015 PhiPsi2015, USTC, Hefei, China 1 The B Factories A e + e - collider runs at Y(4S) resonance to produce

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SLIDE 1

The Belle II Experiment and SuperKEKB Upgrade

Wang, Boqun (University of Cincinnati) On Behalf of Belle II Collaboration September 26, 2015 PhiPsi2015, USTC, Hefei, China

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SLIDE 2

The B Factories

Belle/KEKB at KEK (Japan) BaBar/PEP-II at SLAC (USA)

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A e+e- collider runs at Y(4S) resonance to produce B meson pairs.

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SLIDE 3

Physics Highlights

  • Collected ~1.5 ab-1 of data
  • Measurement of the Unitarity triangle,

and CKM parameters

  • Observation of direct CP violation in B

decays

  • Observation of D meson mixing
  • Observation of new (X, Y, Z) hadrons
  • Search for rare tau decays
  • Constraints on new physics
  • Direct searches for light Higgs, dark

photon, etc.

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SLIDE 4

Super-KEKB

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Target integrated luminosity for Belle II/SuperKEKB: ~50 ab-1

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SLIDE 5

How to achieve 40x luminosity

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  • Nano beam:
  • Small current increase (2-3x)
  • Smaller βy* (20x) via

superconducting focus magnets

  • Challenge of beam

backgrounds

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SLIDE 6

Belle II Detector

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SLIDE 7

Belle II: VXD

= +

VXD

PXD: 2 layers of DEPFET SVD: 4 layers of DSSD

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SVD Beam Test Results

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SLIDE 8

Belle II: CDC

  • Belle II CDC will be larger

than Belle CDC with smaller cells

  • Improved p and dE/dx

resolution

  • Stringing completed in

January 2014 with 51456 wires

  • Commissioning with

cosmic rays

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SLIDE 9

Belle II: TOP

  • The imaging Time of Propagation sub-

detector (TOP or iTOP) will be used for particle identification in the barrel region

  • f Belle II
  • Each TOP module consists of two

quartz bars, one mirror, one prism, and an array of photo-detectors to collect Cerenkov photons from charged tracks

  • To distinguish between kaons and

pions, the photo-detectors should have excellent position and timing resolution

  • This is achieved by using MCP-PMTs

and new waveform sampling electronics

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SLIDE 10

Belle II: TOP

  • TOP modules have been tested at beam test at SPring-8 LEPS in 2013, and

good agreement between data and MC simulation has been obtained, with timing requirement ~O(100ps)

  • 9 out of 16 modules have been assembled (the optical and mechanical

parts). The assembly of the 10th module is on going in KEK

  • Commissioning with cosmic rays is under way

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SLIDE 11

Belle II: ARICH

  • Aerogel Ring Imaging

Cerenkov (ARICH) detector will be used for particle identification in the forward end cap

  • 420 Hybrid Avalanche

Photo Detectors (HAPD), each with 144 channels

  • Two layers of aerogel lead

to better photon yield, while not affecting resolution

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Aerogel Structure

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SLIDE 12

Belle II: ECL

  • Upgrades for high

backgrounds:

  • Barrel: CsI(Tl) crystals

reused, new electronics for waveform sampling

  • Endcaps: old crystals

refurbished, bias filter is modified

  • Cosmic ray test is on going

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Expected Performance

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SLIDE 13

Belle II: KLM

  • Endcaps and parts of the barrel

KLM RPCs of Belle will be replaced with scintillators due to increased backgrounds expected in Belle II

  • Barrel KLM was the first sub-

detector to be installed in Belle II

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Scintillators for barrel and endcap

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SLIDE 14

Physics Opportunities

  • Potential signals for new physics:
  • Flavor changing neutral

currents

  • Probing charged Higgs
  • New sources of CPV
  • Lepton Flavour Violation

decays

  • Dark sectors
  • Belle II physics programme will

be complementary with LHCb.

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SLIDE 15

Summary of Belle II Physics

BELLE2-NOTE-0021

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SLIDE 16

Direct CPV in D0 → Φγ, ρ0γ

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  • Direct CPV in radiative decays can be enhanced to exceed 1%:
  • D

→ Φγ: ACP up to 2%

  • D

→ρ γ: ACP up to 10%

  • D

→ Φγ: first observation by Belle with 78 fb

  • 1

:

  • Yield:
  • relative error on yield ~25%
  • ACP sensitivity at 50 ab
  • 1

: ~1%

Refs:

  • G. Isidori and J. F. Kamenik, PRL

109, 171801 (2012)

  • O. Tajima et al. (Belle Collaboration),

PRL 92, 101803 (2004)

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SLIDE 17

D0 → γγ

  • SM predictions with long distance

effects domination: BR ~ 10-8

  • BaBar with 470 fb-1: BR < 2.2 × 10-6

@ 90% CL

  • Belle II with 50 ab-1:
  • depends on how background

behaves

  • UL ~ 2 × 10-8, if UL scales with L
  • UL ~ 2 × 10-7, if UL scales with √L

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SLIDE 18

τ Lepton Flavour Violation

SM prediction: BR(LFV) ~ 10-25

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Possible NP in LFV:

  • slepton mixing
  • H++ Zee-Babu

models

  • Neutral Higgs boson
  • Majorana neutrinos
  • Seesaw

mechanisms

Belle II Flavour Prospects (B2TiP 2014)

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SLIDE 19

Dark Sector

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  • Dark matter suggests dark

sector.

  • Dark photon: A’, to be in

MeV ~ GeV mass.

  • Probing method:
  • Leptonicaly decaying

dark photons through mixing.

  • Sub-GeV dark matter in

invisible decays.

Current and projected limits, radiative production

  • f dark photon, decay to SM particles (C. Hearty,

B2TIP 2014)

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SLIDE 20

Schedule

Installation and commissioning plan Luminosity schedule

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SLIDE 21

Belle II Collaboration

~600 collaborators, 97 institutions, 23 countries

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SLIDE 22

Summary

  • B-factories had some rich and successful physics

results and many hints of new physics.

  • Belle will be upgraded to Belle II to further explore

these opportunities.

  • Belle II will start operation in 2016 and start taking

physics data in 2018.

  • The target integrated luminosity for physics data is 50

ab-1, which is much larger than the current data set.

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